There is a growing need for new antibiotic agents for the treatment of bacterial infections in animals, and in particular there is a need for new agents which overcome increasing bacterial resistance to existing antibiotics.
Florfenicol is a broad spectrum phenicol antibiotic used exclusively in veterinary medicine. Phenicol antibiotics as a class are potent inhibitors of bacterial protein biosynthesis. Florfenicol has a broad spectrum of activity against many gram-negative and gram-positive bacteria, and is useful in the prevention and treatment of bacterial infections due to susceptible pathogens in birds, reptiles, fish, shellfish and mammals. An important use of florfenicol is in the treatment of respiratory infections in cattle, such as those caused by, for example, Mannheimia haemolytica, Pasteurella multocida and Haemophilus somnus. Effective treatment of bovine respiratory disease (BRD) plays a significant role in reducing what is otherwise one of the leading causes of economic loss to both the dairy and beef industries worldwide.
Reports in recent years indicate that bacterial resistance to florfenicol is developing and has been observed across multiple bacterial genera and species, such as Salmonella (Bolton, L. F., et al., Clin. Microbiol., 1999, 37, 1348), E. coli (Keyes, K., et al., Antimicrob. Agents Chemother., 2000, 44, 421), Klebsiella pneumoniae (Cloeckaert, A., et al., Antimicrob. Agents Chemother., 2001, 45, 2381), and in the aquacultural pathogen, Photobacterium damselae subsp. piscicida (formerly Pasteurella piscicida) (Kim, E., et al., Microbiol. Immunol., 1996, 40, 665). In light of the increasing threat of florfenicol resistance and the apparent mobility of the resistance genes across bacterial species and animal hosts (Cloeckaert, A., et al., Antimicrob. Agents Chemother., 2000, 44, 2858), there is an important need for new antibiotics that maintain or surpass the activity of florfenicol, while also overcoming the challenges of florfenicol resistance. The compounds of the present invention represent such an improvement.